The human genome contains at least 500 genes encoding protein kinases. In fact, protein kinase genes constitute about 2% of all human genes. Protein kinases modify up to 30% of all human proteins and regulate the majority of cellular pathways, particularly those pathways involved in signal transduction.
Because of the profound effects on cells, the activities of protein kinases are highly regulated. Indeed, unregulated kinase activity frequently causes disease related to control of cell growth, cell movement and cell death, particularly cancer. A large body of research is currently being conducted to find drugs capable of inhibiting specific kinases to treat a variety of diseases. Some such drugs are already in clinical use, including Gleevec (imatinib) and Iressa (gefitinib). To increase potency and selectivity, irreversible electrophilic inhibitors, which form a covalent bond with a cysteine in the kinase active site, have been developed. Several of these irreversible kinase inhibitors are currently in clinical trials (e.g., neratinib, tovok). Inhibition of proteins through irreversible binding of an inhibitor to the protein, however, often leads to toxicity and/or immunogenic problems when used to treat diseases. Therefore, reversible kinase inhibitors are needed to inhibit kinases while minimizing the risk of toxicity. The present invention addresses these and other needs in the art.